Treat celeriac much like celery in the north, sowing indoors and growing on in exactly the same way. The cautions about low temperatures apply equally to both.
For very early crops, sow the seed indoors the end of February.
Do plant seed .5 cm or so. I say “or so” because I simply lay the seed down on the pot or flat, barely cover it to keep the seed moist (you can almost see the seed) and keep the soil damp.
It doesn’t need darkness to germinate and you’ll see seedlings within 15-21 days depending on soil temperatures.
When to Plant
Transplant outdoors after frost or sow directly into the soil when the soil is quite warm (end of May to early June). Don’t rush this one – plant it last in the queue.
Where to Plant
You can start them in individual pots (2 seeds to the pot and thin to the strongest) if you only want a few but the easiest is to sow the seed directly outdoors.
Plant in full sun in a soil that is high in organic matter and where stress on the plant (watering too much or too little) is eliminated.
How to Plant
Direct sow at 3 seeds every 1.5 -2 cm and thin out the plants to 15 cm apart when the plants are approximately 10-15 cm tall. Sow .6 cm deep.
This is a slow germinator (15 days plus or minus several depending on weather) so it is a great place to mix radish seed with the celeriac as a “marker” seed and harvest the radish to help thin out the celeriac.
If you plant more than one row of this plant (I have absolutely no idea who would eat that much!) 🙂 then plant rows the standard .75 M apart for good air circulation.
Care & Maintenance
Harvest the rounded small turnip-like roots when they are 5 cm in diameter. They taste kind of nut-like and do not require any blanching to make them whitish. If you let them get larger, they get woody.
You can store them if you cut the tops off and cover them with dry sand at temperatures of 2.5-5C.
Don’t store them in the same container or area where you have very strong smells such as cabbage or onion. They’ll quickly pick up that smell.
(all numbers rounded out)
1/4 inch = .6 cm
1/2 inch = 1.3 cm
1 inch = 2.5 cm
6 inch = 15 cm
12 inch = 30 cm
18 inch = 45 cm
36 inch = 91 cm